Follicles, donor zone and hair loss scales

A transplant moves follicles from the donor zone at the back of the scalp to the thinning area. Doctors grade the thinning with the Norwood scale in men and the Ludwig scale in women.

Techniques

From follicle to scalp

What a transplant moves

1. Hair follicle

Each hair grows from a follicle that cycles through a growth phase (anagen) and a resting phase (telogen). In pattern hair loss the growth phase shortens and the follicle miniaturizes. In men, scalp DHT contributes to this change; finasteride lowers it.[1][2][3]

2. Follicular unit

Hair grows in natural groups of 1 to 4 follicles with their arrector pili muscle, nerves and vessels, as shown in Headington's 1984 transverse study of the scalp. The unit is narrowest near the surface, so a punch under 1 mm can remove it in FUE.[1][2]

3. Donor zone

The safe donor zone is the mid-occipital scalp between the upper and lower occipital protuberances, holding 65 to 85 follicular units per cm2. Donor areas under 40 units per cm2 are less suitable. Beard, chest and other body hair are alternatives with less study.[1]

4. Recipient area

Grafts go to the frontal hairline, mid scalp and crown. A conservative hairline is advised. Grafting only the crown is generally avoided because later loss can leave a ring of hair around it.[1][2]

5. Norwood scale (men)

Hamilton classified male pattern loss in 1951 and Norwood revised the scale in 1975 using 1,000 white men. In 1,005 Indian men aged 30 to 50, 58% had pattern loss and 12.9% were at grades IV to VI.[1][2][3]

6. Ludwig scale (women)

Ludwig's 1977 scale grades diffuse thinning on the top of the scalp with the front hairline kept: grade I minimal, II moderate, III severe.[1][2]